I have the same problem. I just bought Acer Aspire 5 A515-56-555H which built-in with Media Tek MT7921 Wifi, but no driver available for Ubuntu.
I use alternative way that I bought a USB dongle "Comfast CF-727B" with Wifi 1300Mbps and Bluetooth 4.2 (2 in 1).
Ubuntu 20.04 able to auto-detect Bluetooth but no default driver for Wifi (RTL8822BU).
I am able to download, compile and install driver (RTL 88x2bu).
You may refer to this article:
If modprob fail with permission error, you may disable UEFI secure boot (https://vovaprivalov.medium.com/fixing-problem-with-missing-wifi-adapter-on-ubuntu-18-04-dec50879a47e):
$ sudo apt-get install mokutil
check SecureBoot status:
$ mokutil --sb-state
If status is "enabled" , you may disable with following command:
$ sudo mokutil — disable-validation
Then reboot laptop
Now enter a temporary password between 8 to 16 digits. We will use this password later. Enter the same password again to confirm. Once it’s done reboot the system and press any key when you see the blue screen (MOK management). Select Change Secure Boot state.
Enter the password you had selected before and press Enter.
Select Yes to disable Secure Boot in shim-signed.
Press Enter key to finish the whole procedure. That’s all.